Remove unnecessary suppression of clippy::assigning_clones

The lint is no longer triggered because of the switch from educe to derivative.
educe generates an implementation of Clone::clone_from for every non-Copy struct and enum.
derivative only generates one if explicitly requested.

The false positives may have been fixed in rust-lang/rust-clippy#12756.
The fix did not make it into Rust 1.79.0 or Rust 1.80.0.

Author: weekday-grandine-io

ssz/src/persistent_list.rs

@@ -568,13 +568,6 @@ impl<T, B: BundleSize<T>> Node<T, B> {
 
         loop {
             match node {
-                // False positive. See:
-                // - <https://github.com/rust-lang/rust-clippy/issues/12444>
-                // - <https://github.com/rust-lang/rust-clippy/issues/12460>
-                // - <https://github.com/rust-lang/rust-clippy/issues/12467>
-                // - <https://github.com/rust-lang/rust-clippy/issues/12749>
-                // - <https://github.com/rust-lang/rust-clippy/issues/12757>
-                #[allow(clippy::assigning_clones)]
                 Self::Internal {
                     left, left_height, ..
                 } if B::depth_of_length(length) <= *left_height => {